1. Field of the Invention
The present invention relates to a thin film magnetic head.
2. Discussion of Background
In recent years, most thin film magnetic heads that are employed in magnetic disk apparatuses constituting storage systems for computers, are combined type thin film magnetic heads having a thin film write element and a magnetoresistive (hereafter referred to as MR) read element, which achieves a high degree of resolution without depending upon its speed relative to the magnetic disk. Such magnetic head includes a first shield film, a second shield film and an MR element. The first shield film and the second shield film are separated over a distance from each other via an appropriate non-magnetic insulator, with the MR element provided between the first shield film and the second shield film.
An inductive electromagnetic transducer is employed as a write element, and is laminated on the MR read element. The inductive thin film magnetic transducer constituting the write element is provided with a first magnetic film that also functions as the second shield film for the MR read element, a second yoke, a gap film and a coil film supported by an insulating film constituted of an organic resin and the like.
The front ends of the first magnetic film and the second yoke respectively, constitute a first pole tip and a second pole tip that face opposite each other over the gap film having a very small thickness, and write is performed at the first pole tip and the second pole tip. The yoke of the first magnetic film and the second magnetic film are linked with each other at the back gap portion located at the opposite side from the first pole tip and the second pole tip, to complete the magnetic circuit. The coil film is formed wound around the linking area of the yoke in a coil.
In order to achieve a high recording density by employing this type of thin film magnetic head, the quantity of data stored per unit area of the magnetic disk (surface density) must be improved. Improvement in the surface density, as well as improvement in the performance of the write element, is achieved by improving the performance of the magnetic recording medium such as a magnetic disk, and through operating the write circuit at a higher frequency.
One of the means that may be employed to improve the surface density by improving the capability of the write element is to reduce the length of the gap between the poles. However, there is a limit to how much the gap can be reduced, since such a reduction results in a reduction in the magnetic flux intensity between the poles.
Another means that may be employed to improve the surface density by improving the capability of the write element is to increase the number of data tracks in which data can be recorded at the magnetic disk. Normally, the number of tracks that can be recorded at a magnetic disk is expressed as TPI (tracks per inch). The TPI capability of a write element can be improved by reducing the head dimensions that determine the data track width. This head size is normally referred to as the head track width.
Since the first magnetic film at the write element is also used as the second shield film of the MR read element in a conventional thin film magnetic head in the prior art described above, the track width of the first pole tip cannot be reduced, and thus, a rather large side fringing magnetic field is generated during recording. This magnetic field is caused by a leak of the magnetic flux from the second pole tip where the track width has been reduced to the first magnetic film where the track width has not been reduced. Such a side fringing magnetic field places a limit on how much reduction can be achieved for the minimum track width and ultimately places a limit on the degree of improvement in track density that can be achieved. It also degrades the off-track performance when the track data that have been written are read by the MR element.
As a means for solving the problems discussed above, Japanese Unexamined Patent Publication No. 262519/1995 and Japanese Unexamined Patent Publication No. 225917/1995 disclose a means for matching the track width at the first pole tip with the narrow track width at the second pole tip through ion beam milling.
Japanese Unexamined Patent Publication No. 28626/1994 discloses two manufacturing methods. In the first manufacturing method, after forming a first magnetic yoked layer (first yoke), a photoresist layer is applied and then an opening portion is formed at the photoresist layer for pattern forming a magnetic pole end assembly comprising a first pole tip, a gap film and a second pole tip. Next, after forming the magnetic pole end assembly at the opening portion, the photoresist layer located at the front portion of the magnetic pole end assembly is removed. Then, hard baking is performed on the photoresist layer to form a flattened insulating layer. After this, a coil structure, an insulating film and the like are constituted by employing a method in the prior art, and then a second magnetic yoked layer (second yoke) is formed.
In the second method, after a first magnetic yoked layer (first yoke) is formed, a photoresist layer is applied, an opening portion is formed at the photoresist layer for pattern forming a magnetic pole end assembly comprising a first pole tip, a gap film and a second pole tip and the magnetic pole end assembly is formed within the opening portion. After this, a coil structure, an insulating film and the like are constituted, and then a second magnetic yoked layer (second yoke) is formed.
However, the publications of the prior art mentioned above only disclose a technology for improving the surface density by reducing the pole width at the write element, and do not disclose the structure of a thin film magnetic head that achieves superior performance when recording onto a magnetic recording medium having a high coercive force. In addition, they do not disclose a means for prevention of eddy current loss and the like required when the write circuit operates at a higher frequency.